The First Rule of Time Travel
by TinMother
Summary: The first rule of time travel is to never get caught. Don't see anyone, touch anything, change anything. Terrible things happen to people who play with time. Unfortunately, it's rather unlikely the temporal displacement of the entire DA will go unnoticed.
1. The Room

The Room of Requirement was not perfect. It was fairly close, having been constructed by Merlin himself, with Hogwarts later built around it and adapted to suit the magic it radiated. It was said to be one of the Eleven Wonders of the Magical World, but no one is quite sure as the last person to know more than three of them, Manal Haddad of the 14th century, died without passing her knowledge on. It is a room unbounded by space or time, unique in the universe as far as the ministerial arithmancers can tell. It is capable of creating anything conceived by its occupants. But still the Room is imperfect. It bears two major faults.

Firstly, that the Room has very little power to check itself, or prevent its own abuse. It is very nearly a miracle that some nefarious or simple-minded student hasn't wandered in and asked for a creative new plague, or a second big bang. Nearly miraculous, because it was not the work of a divine being, but of a careful network of ghosts monitoring knowledge of the Room, and requesting obliviation for those students with ill intent or unwatched tongue. It was a fine line they walked, but often enough students dismissed the full potential of the Room, and kept it as a private recreational space. Most never found the Room to transform beyond a cozy lounge, for privacy and hominess were so often the chief desires in a crowded boarding school. Most headmasters never need be informed of the Room. In recent years, relative for a ghost of course, they had discovered that they could ask the Room for help when even the headmaster proved untrustworthy, though this method had been generally avoided after Peeves accidentally revivified himself. He'd never really been the same since the odd suicide that began his second unliving. But I digress. Suffice it to say that the Room had been kept relatively far enough from the Hogwarts' rumor mill that no one, not even the ghosts, ever discovered the second problem of the Room of Requirement,

The Room of Requirement seldom contained multiple individuals within its walls. Even when it did, the groups that came usually entered with a common goal for the Room in mind, be it a study space, a private kitchen, a less drafty shack whose shrieks were far more pleasurable. Once even a spelunking cave, designed to be the perfect depth to push older brothers into, had only the unfortunate first year possessed enough arm strength to shove them. Scarcely three dozen groups of more than five individuals had entered the Room, for all its history, and always with a consistent agenda. So it came to be 1996, with no one knowing or having considered what happened when the Rooms occupants disagreed.

And disagree they did. The moment the distinguished, or, at least, thoroughly distinguishable, undersecretary's bombardia rocked the doors to DA headquarters, all common primary desires, to practice defense safely and secretly, vanished. In that absence, a plethora of secondary desires emerged into primacy. Desires from without the Room to be within and within the Room to be without, but not without because there seemed to be an incensed pink toad seething pleasantly in the corridor. Desires for this to not be happening, to be home with parents, to be safe, and not at war, and not the chosen one, and as far from the Umbitch as possible. Also, from George and Fred, a mournful wish to have brought more prank supplies with them, for if they were to go down, they'd go down fighting, nevermind that the contraband would be further evidence against them.

And so, the Room of Requirement did its ever best to accommodate the desires of its thirty odd patrons, as well as the Inquisitors waiting impatiently in the hall. So it was that the doors of the Room opened. So it was that Dolores Umbridge came to enter an empty Room. So it was that she, Mr. Filch, several Slytherins and an innocent cat came to be covered by copious amounts of hive-inducing cranberry pie filling. So it was that the thirty odd students who comprised the DA vanished from Hogwarts, never to be seen again.


	2. Dinner

They'd been found out. The jig was up. That was the only thing that sound could mean and everyone in the room knew it. For who else could it be but Umbridge blasting at the stone wall which concealed their classroom's door, and what else could it mean but swift and painful punishment, likely expulsion, when she eventually broke through. So the students waited, shocked still by fear, for the inevitable next blow to bring the already shaking wall down. Seconds grew to minutes and then larger still, as frightful hesitation dragged their true temporal meaning away, leaving only a cruel vastness, occupied solely by fret's tension.

It was Dean who finally thought to ask the room for a peephole to look into the corridor. He crept toward the wall under the hollow gazes of his classmates. Glancing out, he startled back at a phantom image of Umbridge lurking outside, before peering deeper to find the hallway empty. After a minute, Harry confirmed this on the Marauder's Map, but still no one moved. The strain of stillness soon got to be too much for young Nigel Wolpert, and he voiced the question on everyone's mind.

"What do we do now?"

"Well," Hermione answered, when no one else would, "there are two options. First, that the banging was Umbridge, but she couldn't get in. We've known that they've known where the room is for weeks. Since the door's held and there's no one outside, she's likely given up and will soon pursue another strategy, in which case we can't stay here. If she does a head count and finds us missing, it's as good as if we handed her the sign up sheet. Or there's option two, that it wasn't Umbridge and her pet Slytherins at the door, in which case it could only have been an ally, likely a teacher or the room itself, trying to warn us. I can't say for sure of what, but it's most likely Umbridge coming, meaning again we need to leave."

"But we can't just leave," Katie argued. "It's like you said. They know where we are, but they can't get in. We're safe here. As soon as we leave the room though, we'll be sitting ducks."

"What if it's a trap?" Justin added. "She knows where we are, and she already has a good idea of who's in DA. She was just waiting for someone to crack. Clearly someone has if she's banging at the door. She's just waiting for us to leave, then she'll spring the trap and do who knows what. She's already using the blood quill. If the ministry gets word there's a group called Dumbledore's Army, she'll have permission to do much worse than that."

"But who would crack?" Ron said, clearly affronted by the accusation of disloyalty. "She's been at it for months and no one has."

"Who's not here?" Justin threw back.

This led to an uncomfortable survey among the occupants of the room.

"Terry. He's been fretting all day about the Arithmancy test tomorrow. Said he was skipping to study."

"Seamus used a skiving snack box to get out of Defense today," Dean said with a chuckle. "Only Flitwick caught him before he could eat the antidote, and he's been stuck in the hospital wing with a mysterious blue rash ever since. Personally, I think Flitwick knew he was faking and this is his punishment for it. Pomfrey and Snape have been giving him all manner of disgusting potions and Snape seems far too happy about it. Seamus said one of them was supposed to contain three different parts of a rat, and that I didn't want to know which."

This prompted a small burst of laughter before Lavender answered next.

"Parvati. We noticed Crabbe and Goyle following us, hiding behind pillars half as thick as they were and thinking they were sneaky. She said she'd distract them and I should go ahead. No reason for us to both miss. She never showed up so either she got caught or couldn't shake them. I don't think she'd tell though," she added hastily. "She loved this too much. Said it was the first time she felt really good at anything besides divination and charms."

There was silence after that. They all knew who else was missing, and were waiting for Cho to answer.

"Marietta had detention today," she said quietly, as though speaking to loud would make it real. "With Umbridge. She came back shaking from the last one. Said she was under a lot of pressure, that Umbridge had been talking about getting her father fired, or taking her little brother in for questioning. He's only a firstee. Yesterday, I wouldn't have thought she'd crack, that any of us would… But it's possible."

No one knew what to say to that. They all knew it had happened. They'd felt the same pressure she had and understood. But still she'd cracked, and they hadn't, and now they were done for. No one could voice it, but it was unforgivable.

"But so what if she's told," Hermione all but shouted, unable to properly predict her volume in contrast to the silence. "We can't just stay here. What are we going to do? Skip all our classes, live in this room, _somehow_ feed ourselves, and then sneak off to the train at the end of term. It won't work. We'll have to leave eventually." She paused then, weighing her words. "I'll go. I'll go, then if I get caught, I'll tell you and you can decide what to do. If not, you'll know it's safe to leave."

"No, Hermione—"

"Stop. It was my idea. This whole thing was my idea. If some one should go down for it it should be me." The Weasley twins murmured to each other for a moment, before George stepped forward.

"We'll go with you. We were thinking of ditching out anyway to start our shop. Don't need our NEWTs for that, and the Toads getting more unbearable by the hour. Reckon now's as good a time as any, and if things go South, we've got enough tricks between us to get you out of harm's way.

So it was settled. Harry organized the rest of the DA into groups of three or four, waiting to sneak out when their coins heated with good news. George, Fred, and Hermione, left for the Great Hall. Their stomachs were in no mood to eat and legs markedly upset to be carrying them there, but what else could they do? It was time for dinner.

* * *

They merged with a larger group entering the hall, and made their way unobtrusively to the Gryffindor table. Hermione quickly sent the all clear, signalling for Harry's group to head down, and then began serving herself. She reached for the potatoes before noticing a red-headed first year glaring at her from across the table. She gave the girl a quizzical look. Shrugging, she spooned herself an unnecessarily large portion, and began eating.

"What are you doing?"

Hermione looked up at the indignant girl, before motioning to her food and making the obvious reply, "Eating." She shared a look with Fred before scooping up a bite of ham. She was slicing off a second bite when the girl interrupted again.

"Who're you?" the girl asked, louder this time, her glare joined by that of the curly haired wiaf next to her.

"Hermione." She replied, mock glaring back. She'd barely picked her glass up before the chit spoke up again.

"You can't sit here," She said with the nosy authority of one backed by a rule book. Hermione sighed.

"Look, I'm sorry if you had friends you wanted to eat with. I'll sit somewhere else tomorrow, but for now you'll just have to make due." With that she considered the matter settled, and it was for a good few minutes. Half her plate had been nervously emptied before she was next interrupted.

"But you can't sit here," she said more emphatically, as though the mere act of stressing her words, would make her meaning somehow more clear.

Fred nudged her. Hermione glanced around to see they were garnering a lot of attention. She looked to the head table to see if Umbridge had noticed.

She wasn't there. Neither were Snape, Vector, or Trelawney. This wasn't so much unusual; each were fairly solitary individuals. What struck her was the glare Dumbledore was sending her way, and the dark bearded man who'd stood from his seat on the left end, wand out.

Harry and Angelina entered the hall with Nigel and Romilda in tow, shifting the man's attention. He shouted an unfamiliar orange spell which Harry blocked. Then all hell broke loose.


	3. Some Running

It was a mad house. Hermione, Fred and George immediately sprung up from their table, but luckily so did most of the students, blocking the dark bearded man from firing any further spells. Harry's group had already fled from the great hall, but they weren't far behind, catching up as they neared the stairs to the second floor.

Hermione fished in her pocket for her coin, and quickly flared a message to get back to the Room of Requirement. They were rounding the corner to go up to the third floor when the staircase beneath them jerked from it's moorings. They quickly leapt back onto the second floor platform and looked around to see all the other staircases doing the same, moving to hang in the middle of the tower, unattached.

"It's Hogwarts protocol," Hermione murmured absentmindedly. "When Hogwarts is under attack the headmaster can order the stairways not to move for non-staff members, in order to trap invaders. Hogwarts: A History, Chapter Eleven," she swallowed, "Hogwarts at War."

"What's going on?" Ginny called down from above. She was trapped on the fifth floor with Anthony and Zacharias, who were hastily tugging a panicked Dennis back onto the platform. He'd not quite made the jump off the stairway.

"We don't know." George shouted back. "We're under attack and the Professors aren't on our side. Try to get back to the room."

"How? There're no stairways."

"Shit. Um. Fifth floor… Oh, there's a passage behind the Dryad Tapestry that lets out not too far from the broom cupboards. Fly home. Stay low. Be careful and stay safe." A ray of purple magic flew up from below. "Go!"

With that they were running again. They had no clear direction, before Harry had an idea, running ahead and tugging the group into a left turn. "This way."

"Where are we going?" Fred panted, knowing that this hall would only lead them to dead ends or circling back to the useless stairways. He received no reply as Sprout burst around a corner ahead of them, wand bared. Angelina had her stupefied before she could get off a spell, and the group jumped her fallen body without pausing their run.

George dropped a portable swamp behind them to slow any further pursuers, and soon enough a splash was heard behind them. Looking back Romilda saw a pale, bald head glaring up from the mud.

Harry made an abrupt right, and the group burst into Myrtle's bathroom, causing the ghost to shriek.

"Someone's here. Someone's here. Intruders in my bathroom. Help! Get out! Please!" Harry paid no mind, shouting the word to open the tunnel into the pipes and shoving Nigel down when the opening was large enough. Hermione tried to placate the ghost, get her to recognize them, but the half mad ghost kept screaming, disappearing into the hallway to do it unmolested.

Angelina hurled a reducto down the hall from her cover in the doorway, before retreating as the twins threw out a particularly nasty firework. They slammed the door and George jumped down the tunnel with a terrified, clinging Romilda in his arms. Fred followed next with Angelina. The door exploded open. Harry grabbed Hermione by the arm, yanking her down the tunnel with him. He shouted for the sinks above to close as they fell.

They landed in a heap at the bottom. A moment later, they heard the last sink fall into place above them.

* * *

A barrage of spells could be heard, battering the sinks that held the passage closed, but the chamber had been designed by Slytherin himself. Not even the headmaster could damage the wards he'd placed.

Realizing the door would hold, Harry pulled out the map. He could see the shoemarks of Ginny, Anthony, Dennis, and Zacharias dragging docilely behind Flitwick and McGonagall towards Dumbledore's office. They'd been captured, and were likely being levitated, judging by their lack of movement. On the seventh floor, he saw Hannah and Ernie's marks vanish into the wall he knew hid the Room of Requirement. They were being pursued by someone called Slughorn, but he appeared to be too slow to follow before the doors shut.

Their pockets warmed with a message.

 _ **-What's happening-**_ To which Harry replied.

 _ **-Don't know- Under attack from staff- Dumble not on our side- Strangers here: Aurors? DE?- Safe in chamber of S- Ginny's group captured-**_

 _ **-Why? Umbridge? Ministry?-**_

 _ **-Don't know; didn't see Toad-**_

 _ **-What do we do?-**_

 _ **-Stay in room, we'll come-**_

 _ **-Who is this-**_

DA members throughout the castle swore and dropped their coins. The communication between Ron and Harry ceased. They all knew that handwriting and what it meant. Albus Dumbledore had found a Galleon.

 _ **-Who are you- We have your friends- Surrender peacefully- We will find you-**_

Hermione had to look away. How could this have happened? Why was Dumbledore against them? Who was the bearded man at the head table? Her thoughts were swirling as her brilliant mind tried to process this bizarre turn of events. Suddenly she was struck by the image of the rude red headed child who sat across from her at dinner. She'd seen her before. In a daze she pulled out her wand.

"Tempus"

The room stared as blue letters sketched themselves across the air before Hermione.

6:24 PM, October 13, 1971

* * *

How had this happened, Albus Dumbledore wondered, sitting behind his desk. Before him lay four bruised, unconscious children, the youngest only twelve, sprawled across his red leather armchairs, for all appearances sleeping peacefully.

His staff would be in shortly. They had finished searching the castle and found no trace of the rest of the fake students. They could breach neither the room beneath Myrtle's toilets nor the one on the seventh floor, though wards had been set to warn him should anyone come in or out.

This was disaster. There were at least two dozen, if Horace's estimates were to be believed, unknown children, dressed as students, who had somehow broken into his castle. Most of them still, somehow, remained at large, demonstrating knowledge of Hogwarts superior to even his own.

It could only be Tom's work, for only Tom could have granted them access to what he now realized was Slytherin's chamber. It didn't sit well with him, waiting for the children to come out, only hoping they didn't bring the mysterious monster with them.

Myrtle had been so terrified, she'd left her bathroom for the first time in thirty years. The ghosts were trying to get her out of the owlery now, or to at least get her report of events.

But why would Tom do it. From what he'd seen, Tom's focus was on slowly accumulating power and followers. This made no sense. The move came out of nowhere with no clear goal. His pseudo-students had failed, quite predictably, to blend with the student body. No one was seriously harmed. Nothing appeared to be stolen. The worst damage inflicted was a bump on Pomona's head, and an odd mud pit, whose spellwork showed no signs of deteriorating in the near future. What could he possibly have meant to achieve by this? Had he succeeded or was this only the first move in some larger gambit? Was it simply a distraction?

Nothing about it struck him as logical.

His staff would be in shortly. They would interrogate the four children they had, then notify the ministry of what he could only call an attack. No one was harmed, as far as he could tell, but what else could he call it. He had twenty-some invaders in a political climate slowly and unobtrusively readying for war. That they were children made no difference.

A light flared over his office door to warn him that the professors were on their way up. He flicked his wand, unlocking the door, and breathed a heavy sigh. It had been an exhausting day, likely the beginning of a very long and tiring week.

* * *

 **A/N: Review!... Constructively. If only because I've always been curious if these messages actually work (but also because validation is extremely gratifying).**


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